208 
REVIEW OF THE PERMIAN FOSSILS. 
remarkable, is not inexplicable, even by reference to such laws of distribution as 
must have resulted from repeated changes of the configuration of the bottom of 
the sea, and other submarine phaenomena, by means of which this species of Cho- 
netes may have been displaced from its western habitat at an early period, and pro- 
pagated towards the east, where, under favouring conditions, it subsequently 
assumed a great development; thus offering the rare example of a species, which, 
changing its region, lived through three great palaeozoic epochs, and was partially 
in existence during a fourth. 
The genus Pentamerus, so characteristic of the Silurian epoch, and which begins 
to be very rare in the Devonian strata, has not hitherto been found in the Car- 
boniferous deposits, and does not reappear in the Permian epoch. Conformably, 
however, with the prevailing evidences of the development of nature, which in the 
modifications of beings at successive periods, seems often to retain some feature 
of the preceding types, the Silurian and Devonian Pentameri are represented in 
the groups which next followed by forms of Terebratulse, which offer in their 
internal arrangement a part of the structure of Pentameri 1 . We here allude to 
the Terebratula Schlotheimi, V. Buch, and T. superstes (nob.). In these species, in 
fact, the dorsal valve is furnished, as in the Pentameri, with two oblique, dividing 
plates, which unite at their base, and are fixed on to a vertical septum that is 
attached longitudinally to the central portion of the shell. These singular Tere- 
bratulse of the Carboniferous and Permian deposits, which thus replace the Pen- 
tameri, disappear in their turn at the close of the Palaeozoic age. The Terebratula 
Schlotheimi, we may here observe, presents the remarkable peculiarity, that in Russia 
it belongs exclusively to the Carboniferous rocks, in two localities of which it has 
been detected ; whilst in England and Germany it is a characteristic fossil of the 
Magnesian Limestone and Zechstein. 
The Permian deposits do not contain more than nine species of Terebratulae which 
have been correctly determined, five of which are found in the lower Palaeozoic 
formations. The prevailing species are smooth with concentric striae., one only, the 
T. Geinitziana (nob.), which is allied to the T. Thurmanni, being plaited. 
In effect, if the Brachiopods be viewed as a whole, we believe that of upwards 
of 200 species which prevailed during the carboniferous epoch, ten only prolonged 
1 Mr. King, Curator of the Natural History Society of Newcastle-upon-Tyne, with whom we have been 
in correspondence upon this subject, proposes to establish a new genus for these shells under the name 
of Camerophoria (see his forthcoming Description of the fossils of the Magnesian Limestone of England). 
